1. Field of the Invention
The invention relates to a vehicular antenna device and, more particularly, to a vehicular antenna device suitable for preventing noise intrusion and deterioration in reception sensitivity.
2. Description of the Related Art
There exists a vehicular antenna device having a plurality of antennas that are installed in a vehicle as disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 4-77005. This device splits the outputs of the antennas into an AM band and an FM band. The device then combines signals of the AM band, and combines signals of the FM band after phase adjustment of the FM band signals. Therefore, the antenna device is able to secure sufficient AM-band reception sensitivity, and is also able to improve directivity while securing good FM-band reception sensitivity.
In the above-described antenna device, however, the combination of outputs of the antennas is performed at a site that is exposed outside and that is not grounded. Therefore, there is a danger of intrusion of noises from the site of signal combination. Furthermore, as the outer conductor of a coaxial cable connected to the site of signal combination functions as an antenna, there is a danger of leakage of output components from antennas, which may degrade the reception sensitivity, and may change the directivity.